It has already been disclosed that certain halogen-thiophene carboxylic acid derivatives can be employed for controlling plant diseases (cf. EP-A 0 450 355 and WO 95-27 397). However, the activity of these prior-art compounds is not always satisfactory at low application rates.
Furthermore, a number of 5-trifluoromethyl-4-phenyl-thiophene-2-carboxylic esters are already known (cf. Maybridge Chemical Company, Structure List 1996). However, a microbicidal activity of these substances has not been mentioned to date.